The invention relates to an instrument for surgical purposes comprising two working parts displaceable relative to each other and two handle branches pivotable relative to each other, one of the handle branches being connected to the one working part and the other to the other working part such that when closing and opening the handle branches, the two working parts are displaced relative to each other, and one of the two handle branches carrying for pivotable mounting of the other handle branch a bearing shaft, which has regions of different diameter and is axially displaceable such that in the region of the other handle branch a region of larger or a region of smaller diameter is selectively effective, and the other handle branch having a slot for the bearing shaft with a narrower central section and a widened bearing section at one end, the width thereof in the narrower central section lying between the diameter of the two regions of the bearing shaft and having in the circular, widened bearing section a diameter which corresponds to the larger diameter of the bearing shaft, and one of the two handle branches entering articulatedly with a driver into engagement with the one working part when the bearing shaft extends through the widened bearing section.
Instruments of this kind are widely used in the surgical sector, for example, in the form of so-called tubular shaft instruments or biopsy forceps, etc. In order to dismantle these instruments for cleaning purposes and to exchange parts, it is necessary to release the connection between the working parts, on the one hand, and the handle branches, on the other hand. In particular, with very small instruments this is partly rather complicated, as reliable connections are necessary for the transmission of the high forces and are not easily released.
Such instruments are known wherein the operative connection between a handle branch and a displaceable working part is released by the handle branch being designed so as to be longitudinally displaceable in its bearing on the other handle branch so that with the longitudinal displacement, the engagement with the working part is released (DE-U-93 07 622). However, the design thereof is chosen such that upon release of the operative connection between a handle branch and a moved working part, the handle branches are automatically completely released from one another, i.e., the entire instrument is disassembled.
The object of the invention is to further develop a generic instrument such that release of the operative connection between handle branch and working part is possible without complete disassembly of the instrument in the region of the handle branches being necessary.